Combination fan and limit control



Feb. 13, 1940. B. E. SHAW COMBINATION FAN AND LIMIT CONTROL Filed Feb. 21, 1938 2 Sheets-Sheet l Feb. 13, 1940. B, g w 2,190,337

COMBINATION FAN AND LIMIT CONTROL Filed Feb. 21, 1938 2 Sheets-Sheet 2' Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE Electric Switch 00., Goshcn, Ind., a

ration of Iowa Application February 21, 1938. Serial No. 191,645 7 Claims. (01. 200 139) An object of my present invention is to provide a switch structure in which both a limit switch and a fan switch may be operated from a single operating rod and temperature responsive l element.

A'iurther object is to provide, in a single housing, a limit switch and a fan switch and to provide one temperature responsive element operating to rotate a rod extending into the switch housing, which rod carries a pair of cams cooperable respectively with the fan and limit switches for closing the fan switch when the temperature in the plenum chamber or the like oi a furnace rises to a degree suitable for operation of anair ll circulating tan and to shut down operation of the burnerby opening the limit switch when the temperature rises further to a dangerously high degree.

Another object is to provide a novelarrange- I ment whereby the two switches may be mounted relative to the rod on a single bracket and each operated in a desired manner by'a pair of cams during rotation of the rod'in response to diflerent temperatures to eiiect diiierent ppsitions oi rotation of the rod. 7

Another object is to provide a structure of novel character which permits the use of a plurality of switch units such as shown in my co-pending temperature ranges as indicated by the pointer cooperating with the scale.

A further object is to provide a novel connection between the disc having the graduated scale 5 thereon and the thermostatically responsive rod so that connection for the position of the scale relative to the rod may be'made conveniently whenever desired inaddition to initial positioning.

of the disc relative to the rod at the factory so beingv facilitated.

Still a further object is to provide a bracket adapted'to have mounted-thereon a pair of switch units, the bracket to pivotally supportoperatingarmsiortheswitchimitathearms.

a in turn with-the cams iorthe purpose of opening and closing the switches within the switch unit.

Although the invention is susceptible of a variety of embodiments, it is'unnecessary to fully describe-and'illustrate more than one in order to I, give a full understanding of the invention both from its structural and functional standpoints. Accordingly, I have illustrated a preferred and desirable embodiment of *the invention in the accompanying drawings forming a part of this 1.1 specification and throughout the views of which like reference characters refer to the same parts.

Figure l is a plan view, partly in section, of my combined fan and limit switch.

Figure 2 is an enlarged sectional view on the I line 2-2 of Figure 1 showing details of construction particularly with respect to connection of the cams for operating the switches with the rod which is thermostatically controlled.

Figure 2a is an enlarged perspective view of the 20 left end of the rod in Figure 2 showing its con- 4 struction.

I Figure 3 is a front elevation of my control switch with part of the cover broken away and showing the. switch in normal position at approx- 25 imately room temperature.

Figure 4 is a sectional view on the line 4-4 of Figure 1 showing the fan switch cam rotated to a position for turning the fan switch on.

Figure 5 is a similar sectional view on the line 5-5 of Figure 1 showing the limit switch cam rotated to a position for turning the limit switch off.

Figure 6 is a similarview showing the thermostatically controlled rod rotated reversely due to 38 a drop in temperature and resulting in turning on of the limit switch.

Figure'IisaviewsimilartoFlgureishowing the parts returned to a position corresponding to a lower temperature than in Figure 4 and resulting in turning oil? of the fan switch.

.Figures 8 and '9 are perspective views of operating levers for the limit and Ian switches.

Figure 10 is a perspective view of a bracket for supporting the Ian and limit switches.

Figure 11 is a sectional view on the line Il-il of Figure 7 showing the operating levers; and

Figure 12 1s a sectional view on the line I2-II of Figure 2. v

0n the accompanying drawings I have used the reference character C to indicate generally a switch casing. Within the switch casing C, a

bracket B is provided on which is mounted a limit switch L and a fan switch F. The switches L and F are switch units of the character described is I in my patent hereinbefore referred to and include 1 a spring ii at one briefly the following elements (see Figure 5).

A base I0 is provided on which is cover I2. The base and cover are preferably of insulating material. A switch arm I8 is, pivoted on knife edges l4 and is normally constrained to remain in contact therewith due to the action of end of the switch arm and a magnet l8 at the other end thereof. To avoid any possibility of the switch arm disengaging the knife edges l4, fingers I! are bent from the bracket carrying the knife edges l4 and are located opposite the knife edges l4.

The magnet it attracts an armature l8 carried by the switch arm l8. An operating pin i9 is slidably mounted in'the cover i2 and has the spring Q I! interposed between it and the switch arm II. when the switch arm is in the position shown, a projection 20 thereof lifts a movable contact 2| from a stationary contact 22. The contact 2i is carried by a leaf spring 28.

The switch units L and F are secured to the bracket B by screws 24 extending through the units and threaded into the bracket. In this manner the units may be readily removed for repair or replacement whenever desired.

Fbr operating the switch units L and F, I provide operating levers 25 and 26 respectively. Each of the levers is provided with perforated ears 2! pivotally mounted on a, pivot rod 28. The rod 28 extends through a perforated ear 28 then through the ears 21 as shown in Figure 11, and then through a perforation 88 in the front of the bracket B.

The bracket 13 includes a pair of sides 8| which are secured to the back wall 82 of the casing C by means of extensions 88 of the sides provided through slots 84 of the back wall 22 as shown in Figures 10 and 11 and then riveted as at 388. When thus riveted into position, the pivot pin 28 is confined against subsequent displacement from assembled position by reason of its head 85 being confined between the ear 29 and the back wall 32.

The operating levers 25 and 28 have cam engaging projections 86 and 31. The projection 88 is adapted to co-act with a cam 89 for swinging the lever 28. outwardly and thereby depressing the operating pin ll of the limit switch L to oi! position of the switch as shown in Figure 5. The cam has a hub which may be secured to an operating rod 4| by set screw 42.

, The rod 4| is thermostatically controlled by a coiled bimetal element 43 which is located in a plenum chamber or the like of a furnace so as to be responsive to the temperature of the air circulated around and heated by the furnace. One end of the element 43 is secured to the'rod 4| while the other end is secured to a stationary tube 48a. projecting from the casing C.

' The rod has a reduced portion 4|a in the hub 48 and rotatably mounted on this portion is a second cam 44. The cam 44 has a hub 45 and is locked relative to the rod 4| through elements 48, 41 and 48.

The element 46 is a pointer arm having a pointer 49 thereon (see Figure 3).- The pointer is adaptedto cooperate with a graduated scale on the disc 50. The element 41 is a lock nut for locking the pointer arm 46 relative to the sleeve element 48. The sleeve element in turn is locked permanently to the rod 4|a by a set screw 5| threaded into the rod in such manner as to expand the rod to fricticnally engage the bore of the sleeve 48. This is illustrated in Figures 2 and 2a wherein the rod is slotted as indicated at 52 mounted a and has a tapered bore portion 88 to expand the rod as permitted by the slots 52 when the set .screw is tightened.

In order to permit loosening of the pointer arm 48 relative to the sleeve 48, yet retain the graduated disc I8 in predetermined position relative thereto, opposite "sides of the sleeve 48 are formed flat as indicated at 58 and the disc 58 has an opening of such shape as to fit the sleeve. This permits longitudinal sliding, but prevents rotation of the disc relative to the sleeve. Therefore, the position of the disc relative to the rod 4| may be set at the factory and thereafter the nut 41 may be loosened whenever it is desirable to swing the pointer '49 to a different temperature setting on the scale of the disc. The pointer arm 46 is operatively connected with the cam 44 by means of an arm 55 extending from the pointer arm and entering a slot 58 in the cam 44. Thus the cam may be adjusted whenever desired by swinging the pointer arm.

To facilitate setting of both the cam 88 and the sleeve 48 at the factory, the bracket 13 is provided with an indicating arrow 51 whereby the screw 5| may be loosened and the disc set at whatever temperature is affecting the bi-metal element 42 and the screw. tightened for locking the disc in this position.

The position of the cam 88 determines the cut 011 point of the limit switch L. The rod 4| can be .manually rotated until the limit switch is thrown to off position and if thedesired indicia on the disc 58 is not then in register with the arrow 51, the set screw 42 can'be loosened and the cam 88 rotated and again fixed relative to the rod to secure the desired cut out position of the limit switch. My arrangement provides for operation of both the limit switch and the fan switch from a single thermostatically controlled element and adjustment of the fan switch on the job is readily made.

In operation of the switches, the cam has rotated to a position corresponding to about 153 degrees in Figure 4.1 Due to the spring I! in the switch unit F, the operating pin i9 in-Figure 4 moves out to a podtion corresponding to a circumference line "a on the cam 44 before the magnet l8 has suflicient power to overcome the tension of the spring and close the switch which in Figure 4'has just been closed. The limitswitch L, of course,'i s closed and remainssountil a dangerously high temperature is attained as in Figure 5. A second circumference line b" indicates the position of the cam engaging portion of the levers 25 and '28 to secure opening of the Figure 7, the fan switch F will be turned off. It .is thus obvious that the differential of operation of the switch L is about thirty degrees, while that of the switch F is about six degrees. The difference in the differential of operation is secured by having the lobe 39 of the cam 88 spread over a wider circumferential extent of the cam area than the lobe 88a of thecam 44a of the fan switch F. Since these lobes are fixed, the differential of operation of the switches is also fixed, but the range of the fan switch'F may be changed as desired by changing the pointer"!!! relative to the scale on the disc 50.

The limit switch L is connected in circuit with a burner motor or the like in the usual manner, while the fan switch F is connected in circuit with an air circulating fan whereby my switch structure controls both the burner motor and the fan motor, one in response to a dangerously high temperature and the other in response to the temperature desired for operation of the fan.

The desired operation of both switches from one thermostatic element is secured by the construction described in my specification.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I'claim as my invention:

1. In a combined fan and limit control switch, a switch housing, a fan switch and a limit switch mounted therein, an operating rod for said switches, a first cam thereon for operating said fan switch, a second cam thereon for operating said limit switch, a temperature responsive element for rotating said rod, said first cam being rotatable relative to said rod, a disc secured to said rod, a pointer normally fixed relative to said disc, means for swinging said pointer relative to said disc to a new position spaced from the first position and for locking said pointer in its new position and an operative connection between said pointer and said first cam to retain said first cam in relatively fixed position circumferentially of said rod.

2. In a control switch of the character described, a switch, an operating rod for said switch, a cam thereon for operating said switch, a temperature responsive element for rotating said rod, said cam being capable of rotation relative to said rod, a disc secured to said rod and r0- tatable therewith, a pointer normally fixed relative to said disc, means for swinging said pointer relative to said disc to a new position spaced from the first position and for locking said pointer in its new position, said cam having a perforation and said pointer having an extension entering said perforation to effect simultaneous movement of the cam and pointer when moving the pointer to said new position and when the disc and pointer thereafter move together in response to temperature changes.

3. In a combined fan and limit control switch, a switch housing, a fan switch and a limit switch mounted therein, an operating rod for said switches, a first cam thereon for operating said fan switch, a second cam thereon for operating said limit switch, a temperature responsive element for rotating said rod, said first cam being rotatable relative to said rod, a disc normally secured to said rod and operatively connected to said first cam, said disc having a hub on said rod, said hub and disc being rotatable relative to said rod and means for locking the disc in a desired position on the rod comprising an expander member in the portion of said rod extending through said hub, said rod being split to permit expansion thereof to frictionally engage the bore of said hub.

4. In a combined fan and limit control device, a fan switch and a limit switch, an operating rod therefor, a first cam thereon for operating said fan switch, a second cam thereon for operating said limit switch, a temperature responsive element for rotating said rod, a hub on said rod, said first cam being rotatable relative to said hub, means for locking said cam relative to said hub and means for locking said hub in a desired position relative to said rod comprising an expander member in the portion of said rod extending through said hub, said rod being split to permit expansion thereof to frictionally engage the bore of said hub.

5. In a control switch of the character disclosed, a switch housing, a pair of switches mounted therein, an operating rod for said switches, a first cam thereon for operating one of said switches, a second cam, thereon for operating the other of said switches, a condition responsive element for rotating said rod, said first cam being capable of rotation relative to said rod, a disc secured to said rod, a pointer normally fixed relative to said disc, means for swinging said pointer relative to said disc to a new position spaced from the first position and for locking said pointer in its new position and an operative connection between said pointer and said first cam to retain said first cam in relatively fixed position circumferentially of said rod.

6. in a control structure of the character disclosed, a switch, an operating rod therefor, a cam thereon for operating said switch, a tem perature responsive element for rotating said rod, said cam being capable of rotation relative to said rod, a disc normally secured to said rod and cperati'veiy connected to said cam, said disc having a hub on said rod, said hub and disc being capable of rotation relative to said rod and means for locking the disc in a desired position on the rod comprising an expander member in a portion of said rod, said rod being split to permit expansion thereof to irictionally engage the bore of said hub.

7. In a control switch of the character dis-- closed, a switch housing, a switch mounted therein, an operating rod for said switch, a cam thereon for operating said switch, a condition responsive element for rotating said rod, said rod having a shouldered and threaded element therein, a pointer and a disc on the threaded part of said element against the shoulder thereof, said pointer being rotatable and normally fixed relative to said element, said disc being slidable and non-rotatable on the threaded part of said element and against said pointer, means for swinging said pointer relative to said disc to a new position spaced from the first position, a nut on said threaded part of said element for locking said pointer in its new position and an operative connection extending from said pointer to said cam to retain the cam in relatively fixed position circumferentially of said rod.

BURTON E. SHAW. 

